Doing the Tango has paid off for the University of California, Riverside (UCR) and the citrus industry. The Tango mandarin, first released to growers in 2006 after development at UCR, has generated more than $70 million in cumulative economic value for the university. This makes it one of the most successful innovations in University of California history.
Known to consumers under names like Cuties, Halos, and Tango Fruit, this easy-peeling and mostly seedless fruit became popular worldwide as a healthy snack and profitable crop. The expiration of its U.S. plant patent now allows domestic growers to plant Tango without paying royalties. Internationally, however, protections remain in place and royalties will continue from foreign growers.
The Tango’s influence on agriculture is significant. According to the California Department of Food and Agriculture, by 2024 nearly 20,000 acres—32 percent—of all mandarin acreage in California were planted with Tango mandarins. The U.S. Department of Agriculture estimated that during the 2024–25 season, mandarins produced in California had a total production value of $855 million; with Tango accounting for about $272 million.
The variety is now grown in over 20 countries and sold in more than 50 countries worldwide. In January 2026, a European trade association named it “Flavor of the Year” in Spain and Portugal.
“Taking into account the entire supply chain, from nurseries and farms to packers, transporters, and retailers, Tango has revolutionized the citrus industry in its 20 years of existence, generating a significant economic impact each year,” said Brian Suh, UCR’s senior executive director of technology partnerships.
The development began with Professor Mikeal Roose and Timothy Williams at UCR’s Department of Botany and Plant Sciences. With support from the California Citrus Research Board starting in the 1990s, they used gamma irradiation on another mandarin variety’s buds to encourage mutations that could lead to seedlessness—a rare trait achieved much faster through controlled radiation exposure.
Roose explained: “Some genetic changes happen, some don’t. You just have to grow the trees and wait — sometimes for years — to see what you’ve got.”
After several growing seasons testing around 200 trees from irradiated buds grafted onto rootstock—most did not meet expectations—but eventually two promising candidates emerged; one was selected as Tango because it produced fewer seeds.
The key advantage for growers is that both ovules (which develop into seeds) and pollen are highly sterile in Tangos; this means not only do they remain seedless regardless of neighboring varieties but also do not contribute pollen leading to unwanted seeds elsewhere nearby. Growers no longer need costly measures such as nets or isolation to prevent pollination by bees.
“It’s very easy to grow in the nursery,” Roose said. “It works well on the main rootstocks we use, grows vigorously in the field, and produces heavy yields. You do have to manage it carefully so it doesn’t overbear — which is common in mandarins — but otherwise it’s a dream variety for growers.”
Consumers benefit from fruit that peels easily without refrigeration requirements; its firm skin aids shipping globally while late-season harvest extends market availability by two months each year.
“It had all the qualities you want in a mandarin — easy to peel, rich color, great flavor, and very low seeded even when grown near other varieties,” Roose said. “That combination is very rare.”
Williams reflected on their achievement: “You spend years working with hundreds of trees, and then one day there it is — the one that checks all the boxes,” he said. “When you see it in grocery stores and lunchboxes around the world, that’s a pretty good feeling.”
Tango continues UCR’s tradition since opening its Citrus Experiment Station on campus back in 1907; since then more than forty new citrus varieties have been introduced including Oroblanco grapefruit now cultivated globally as a specialty crop.
UCR also maintains biodiversity through resources like its Givaudan Citrus Variety Collection with about 4,500 trees representing over 1,000 citrus types worldwide.
“When you look at Tango’s success,” Williams added,”it’s gratifying — but it also reminds you that we’re just one chapter in a much longer story of citrus improvement at UCR.”
“The challenges facing citrus today — new diseases, climate change,sustainability—are different from those a century ago,but themissionisthesame:tokeepCalifornia citrus viable,val uable,and accessible well into future.”
